This invention relates to a watering device for use in greenhouses and in similar environments.
Uniformity of watering is quite important in intensive cultivation of small plants grown on close spacing, such as is the common practice in greenhouses. Uniformity of watering is particularly important when the watering system is also used to apply fertilizer, as is often done. The present invention relates to a greenhouse watering device in which uniformity of watering, with or without fertilizer, is achieved.
Static arrays of nozzles, in addition to interfering with cultivation, have been unable to distribute water uniformly in two dimensions. A fairly uniform distribution along a straight line can be achieved with linearly arranged sets of nozzles, but in order to provide uniform water distribution over an area, the linear set of nozzles must be moved transversely over the area. Thus, several types of movable irrigators have come into use. Unfortunately, each of these prior-art movable irrigators has significant disadvantages.
In one major type of movable irrigator, a row of nozzles is arranged along a horizontal boom, which extends across the full width of a greenhouse and is fastened in the middle to a carriage or cart which runs on rails or on a concrete walk. The rails or the walk take up a significant amount of valuable ground space in the greenhouse, which could otherwise be used for growing plants: considering the costs of building and maintaining greenhouses, this loss of growing space is an important disadvantage to this type of movable irrigator.
Another movable irrigator eliminates this disadvantage by having the carriage or cart travel along an overhead track. However, in this form of movable irrigator, a large and heavy track is necessary to support the horizontal boom and the water in it, and a substantial overhead structure in the greenhouse is required to support it and make it sufficiently rigid. Furthermore, the cart tends to become twisted in the tracks and to jam. A still further disadvantage is that a massive overhead structure tends to shade the plants growing beneath it, and when the watering device is not in use, the amount of shadow cast can be quite significant.
Another approach has been to support the horizontal nozzle-carrying boom at each end. However, end support requires a very heavy construction for the boom, since its unsupported length is then twice that of a boom supported in the middle. Furthermore, since greenhouse roofs are normally gabled or arched and are therefore higher in the middle, support cables can be run from the ends of a center-supported boom to the higher center structure of the greenhouse roof, while trussing cables for an end-supported boom would have to extend below the boom, absorbing needed space and putting the cables in the path of the water flow. An additional problem with this system is that track space must be provided along both side walls of the greenhouse. Even though such tracks are above ground level and even though plants would theoretically be grown directly under the tracks, in actual fact, this is seldom possible, because cultivating is done with a tractor, and the tires of the tractor must clear the supports. As a result, the growing space in the greenhouse is substantially reduced. End-supported irrigator booms have the further disadvantage that they tend to twist or oscillate as they advance unless both ends are driven, and it is more expensive to drive both ends.
A problem common to substantially all of these movable irrigators is that the water supply hoses are commonly dragged along the ground or else festooned in large loops. Dragging causes excessive wear and also has the disadvantage of taking up a space three or four feet wide for the loop of hose. Here again, the growing space is substantially reduced. Festooning is a complicated solution, requiring a traveling hanger for each loop of hose suspended and, of course, more hose is required with festooning than in the other systems, because the hose can never be fully stretched out, and it must travel the complete length of the greenhouse unless complicated switching is used at the center of the house. In methods where festooning is not required, the hose can extend each way from the center of the greenhouse. Further, the length added by festooning carries a disproportionate penalty, since the hose must be made larger in diameter to keep water friction losses reasonable. Consequently the weight of the water plus the hose that must be supported when the boom is near the supply end is considerable. Also, the space absorbed by the festooned hose is quite large.
Another method of supplying water to booms does away with the hose and provides an open trough into which an elephant snout of the traveling boom reaches to pick up water. In this type of device, a pump on the boom creates the water pressure to supply the nozzles. However, such a trough is much more costly to provide than an equivalent length of hose, and this method includes the further expenses of the pump, a pressure regulator, and so on, which can be a considerable amount. Besides that, the open trough takes up about a foot of growing room from the width of the greenhouse.
An object of the present invention is to solve the foregoing problems and to do so in a relatively inexpensive and a completely reliable manner. It is an object of the invention to provide an irrigating boom which is light in weight, easy to install, and easily operated by an unskilled laborer.
Another object is to provide an irrigating boom which does not require special parts or structures.
Another object is to take up as little growing space as possible and to thereby enable cultivation of substantially the complete extent of the greenhouse.
Another object is to provide a device that shades the growing plants as little as possible and also interferes as little as possible with cultivation by tractor.
A further object that must not be overlooked is the achievement of even distribution of irrigation water within a greenhouse.